A technique has been conventionally known which includes detecting the position of a subject vehicle on the basis of an image captured by a camera and correcting the detected position of the subject vehicle on the basis of a measurement result obtained using the global positioning system (GPS) (see Japanese Application Publication No. JP2014-115247A).
In the above conventional technique, the measurement value obtained using the GPS may significantly vary in some cases, such as when the GPS switches satellites, and an erroneous determination may be made that a lane in which the subject vehicle does not actually travel is recognized as the lane in which the subject vehicle travels.